This invention relates to circuit interrupters, and more specifically relates to a novel circuit interrupter wherein an arc current is circulated within a gas-filled container which is filled with a dielectric gas, such as sulfur hexafluoride.
In accordance with the invention, a novel contact construction is provided which causes the arc current to deflect radially inwardly of the axis of the interrupter in order to be more perpendicular to the magnetic flux produced by a coil in series with the arc and by a circulating current in a ring-shaped arc runner, to increase the Lorentz force on the arc current and to move the arc current radially inwardly and away from the outer contact parts where it could cause a restrike of the arc.
Arc spinner type interrupters are known in the art and are typically shown in U.S. Pat. No. 4,052,577, in the name of Gerald A. Votta, as well as U.S. Pat. No. 4,052,576, in the name of Robert Kirkland Smith.
In prior devices, the arc could bend outwardly and away from the axis about which the arc circulates during interruption because of outwardly directed magnetic forces which are unintentionally applied to the arc. This is because the current which is fed to the circular arc runner has been connected to the arc runner at its inside diameter and produces a bend in the current path which is away from the axis. This has then tended to bend the arc radially away from the axis of the arc runner. Because of this, the arc, where it is closest to the arc runner and where the force for rotating the arc is greatest, is more parallel to the magnetic field than it should be, thus reducing the Lorentz force on the arc. That is to say, the Lorentz force which rotates the arc is the vector cross product of the arc current and the instantaneous magnetic field. When the angle between these two vectors decreases, and they become more parallel, the Lorentz force produced is decreased.
A further disadvantage of the inwardly fed arc runner and its consequent distortion of the arc current radially away from the circulating axis is that the arc current is moved toward the outer separating contacts, thereby to increase the danger of a restrike across the opening contact gap.